Leading Article: As we marvel at a trapped whale and a visiting shark, we plunder the seas

We have a curiously inconsistent attitude toward the sea and its inhabitants, as this week has demonstrated. On one level, we are clearly fascinated by the oceans. Crowds lined Fraserburgh harbour in Scotland this week to catch a glimpse of a trapped young minke whale. The scenes were reminiscent of the frenzy of interest when a bottle-nosed whale swam up the Thames last year.

At the other end of the country, the rumours that a great white shark was patrolling the waters off Cornwall provided a dubious thrill for holidaymakers. Another ancient fish has captured scientists' imagination, too, this week, with the news that a coelacanth has been hooked in Indonesia. Scientists previously thought the fish group had died out about 70 million years ago. Finally, the Russian aquatic exploits deep beneath the North Pole piqued the public's interest, proving that there is a romance and mystery surrounding ocean exploration that has a unique ability to inspire.

But for much of the time we seem uninterested in the plight of the sea. Most news concerning our oceans is troubling these days. Cod stocks in British waters have been destroyed by intensive fishing. Fisherman are now going after deep-sea fish to maintain yields, despite the disastrous consequences of bottom-dredging for the ocean's ecology. A major study involving an international team of marine scientists warned last year that if global fisheries continue to decline at the present rate, they will be utterly wiped out by the middle of the century.

The plight of the big charismatic beasts of the ocean is worrying too. All those excited about the possibility of a UK visit from a great white might like to bear in mind that the animal is officially endangered thanks to overfishing. Many species of whale remain under threat too - something that seems to be of little concern to the governments of Norway and Japan which wish to relaunch commercial whaling.

Another vital element in ocean ecology is coral. Reefs are being destroyed by the rising acidity of the seas, a consequence of its absorption of man-made carbon dioxide emissions. And then there is the sheer negligent vandalism of the oceans by industry and commerce to consider. Rubbish - much of it plastic - is dumped into the seas with abandon. A study revealed earlier this month that some 6.5 million tons of rubbish lie below the surface of the world's oceans, with the highest concentration by far in the Mediterranean. Scientists are predicting that this detritus is set to make an unwelcome reappearance when the oceans are churned up this century by more powerful storms as a result of climate change.

Yet such reports do not seem to inspire the same sense of urgency as stories about the habitats of land animals being destroyed by intensive farming or areas of natural beauty being disfigured by rubbish. The truth is that we have a naive belief that the sea can look after itself. This is profoundly mistaken. The oceans are just as sensitive to the hand of mankind as the land. If we fail to treat it properly by protecting fisheries, outlawing bottom trawling, clamping down on the dumping of plastics and acting to preserve our coral reefs, we will reap an increasingly bitter aquatic harvest.

We must hope that one of the rare bits of oceanic good news of late - Birds Eye's decision to switch from cod to pollock in its fish fingers - represents a growing acceptance that we cannot exploit our seas, and its inhabitants, in so destructive and negligent a manner.

Rushing to the waterside to catch a glimpse of a whale or a shark is a pleasant enough diversion for the holidays. But it is time we all took a deeper interest in the condition of our oceans.